This section provides background information related to the present disclosure which is not necessarily prior art.
For example, Japanese Utility Model Laid-Open No. 6 (1994)-49856 discloses a typical conventional sealing device for tight sealing between engine oil and clutch oil in a wet type engine.
FIG. 16 is a half cross-sectional view illustrating a conventional sealing device 100 which is similar to a device illustrated in FIG. 5 in the above-described patent document. That is, the sealing device 100 is made of a rubber-like elastic material and formed in an annular metal case 101 which is pressed-in and fitted to an inner peripheral face of a housing 120. The sealing device 100 includes a pair of radial seal lips 102 and 103 which are positioned oppositely to each other in the axial direction. Extension springs 104 and 105 for giving fastening force to a rotary shaft 130 are mounted on outer peripheries of the radial seal lips 102 and 103. The one radial seal lip 102 is for sealing engine oil, and the other radial seal lip 103 is for sealing clutch oil.
However, as for the sealing device 100 illustrated in FIG. 16, the radial seal lips 102 and 103 have the comparatively short life since being abraded by the fastening force to the rotary shaft 130. Further, when the radial seal lips 102 and 103 are mounted in the slight eccentric state to the rotary shaft 130, parts at circumferential directional sides of the radial seal lips 102 and 103 have too low sliding face pressures to the rotary shaft 130 or some spaces between these seal lips and the rotary shaft 130 are generated, so that different liquids at both axial sides may be mixed each other. Further, when the radial seal lips 102 and 103 are fitted on the rotary shaft 103 to be mounted, meticulous care is needed not to damage the radial seal lips 102 and 103.
Further, for solving such the problem, an end face sealing type end face sealing device as illustrated in FIG. 1 in the above-described patent document has been developed in recent years. In this end face sealing device, a seal lip is slidably contacted with an end face of a slinger which is vertical to an axis of a shaft. However, as for the end face sealing type, a negative pressure is caused in the seal internal space by centrifugal force at the time of rotation, where the space is tight closed by both seal lip sliding parts. Thus, the seal lip is entirely contacted with the end face of the slinger so as to increase sliding load. As a result, sealability may be decreased.